The invention relates to a lens for illumination purposes, in particular a lens for a headlamp for projecting the light emitted by a light source and possibly reflected by a reflector in order to produce a predefined illumination pattern.
The invention relates further to a method of producing a lens, in which the lens is produced in a production method which operates intermittently or cyclically.
The invention further relates to a method of marking a lens with a code.
Since the mid-80s, for cars in the upper and upper-middle-class, what is known as a “poly-ellipsoid headlamp” (PES) has been offered which, instead of the diffuser disc, has a plane-asphere as a lens, which is matched with a threefold ellipsoid reflector or, in recent times, also with free-form surface reflectors.
The basic structure of such headlamps is known and can be gathered from DE 198 14 480 A, for example. Such a PES head-lamp comprises a reflector which consists of a section of an ellipse and has a single light source, which is arranged in the region of the first focus of the reflector. In this headlamp, a plane-convex lens is provided at a distance from the reflector, its focus lying in a region of the second focus of the reflector. Inserted in between the reflector and the plane-convex lens is a mask, which is positioned in a region of the second focus of the reflector. It has an appropriately adapted shape in order that the bundle of light emerging from the head-lamp satisfies the prescribed light-dark limit.
Because of the stipulations relating to quality control in the car industry, which are increasing more and more in recent times, the quality requirements which are placed on such lenses increase continuously.